This invention relates to a filter formed of a metal plate mounted e.g. in a hole as a liquid passage for removing any foreign matter in the liquid, a piston pump having a discharge valve including a valve seat member in which the abovementioned filter is mounted, and a method of mounting the filter in the valve seat member of the piston pump.
Among pumps mounted in brake hydraulic pressure controllers as their sources of hydraulic pressure for driving them, piston pumps (also called plunger pumps) are most popular. JP patent publication 2003-528244 discloses such a piston pump.
The piston pump disclosed in this publication includes a discharge valve comprising a valve body and a tubular valve seat member having a bottom and formed with a filter mounting recess (hole) having an opening facing a pump chamber. A filter is mounted in the filter mounting recess so that brake fluid flows through the filter. The filter disclosed in this publication is a molded product which also serves as a spring retainer and includes a cylindrical portion. Thus, this filter has to be formed by drawing, i.e. pressing, which is less productive and thus costly. The filter further includes a flange at one end of the cylindrical portion only and has no such flange at the other end. Thus, the filter can only be pushed into the filter mounting hole with the other end of the cylindrical portion first and not the other way around. This makes it difficult to mechanize the steps of mounting such a filter into the filter mounting recess.